Internet Engineering Task Force (IETF) M. Jones
Request for Comments: 7523 Microsoft
Category: Standards Track B. Campbell
ISSN: 2070-1721 Ping Identity
C. Mortimore
Salesforce
May 2015
JSON Web Token (JWT) Profilefor OAuth 2.0 Client Authentication and Authorization Grants
Abstract
This specification defines the use of a JSON Web Token (JWT) Bearer
Token as a means for requesting an OAuth 2.0 access token as well as
for client authentication.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7523.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Jones, et al. Standards Track [Page 1]

RFC 7523 OAuth JWT Assertion Profiles May 2015
definition of additional authentication mechanisms to be used by
clients when interacting with the authorization server.
"Assertion Framework for OAuth 2.0 Client Authentication and
Authorization Grants" [RFC7521] is an abstract extension to OAuth 2.0
that provides a general framework for the use of assertions (a.k.a.
security tokens) as client credentials and/or authorization grants
with OAuth 2.0. This specification profiles the OAuth Assertion
Framework [RFC7521] to define an extension grant type that uses a JWT
Bearer Token to request an OAuth 2.0 access token as well as for use
as client credentials. The format and processing rules for the JWT
defined in this specification are intentionally similar, though not
identical, to those in the closely related specification "Security
Assertion Markup Language (SAML) 2.0 Profile for OAuth 2.0 Client
Authentication and Authorization Grants" [RFC7522]. The differences
arise where the structure and semantics of JWTs differ from SAML
Assertions. JWTs, for example, have no direct equivalent to the
<SubjectConfirmation> or <AuthnStatement> elements of SAML
Assertions.
This document defines how a JWT Bearer Token can be used to request
an access token when a client wishes to utilize an existing trust
relationship, expressed through the semantics of the JWT, without a
direct user-approval step at the authorization server. It also
defines how a JWT can be used as a client authentication mechanism.
The use of a security token for client authentication is orthogonal
to and separable from using a security token as an authorization
grant. They can be used either in combination or separately. Client
authentication using a JWT is nothing more than an alternative way
for a client to authenticate to the token endpoint and must be used
in conjunction with some grant type to form a complete and meaningful
protocol request. JWT authorization grants may be used with or
without client authentication or identification. Whether or not
client authentication is needed in conjunction with a JWT
authorization grant, as well as the supported types of client
authentication, are policy decisions at the discretion of the
authorization server.
The process by which the client obtains the JWT, prior to exchanging
it with the authorization server or using it for client
authentication, is out of scope.
Jones, et al. Standards Track [Page 3]

RFC 7523 OAuth JWT Assertion Profiles May 20151.1. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Unless otherwise noted, all the protocol parameter names and values
are case sensitive.
1.2. Terminology
All terms are as defined in the following specifications: "The OAuth
2.0 Authorization Framework" [RFC6749], the OAuth Assertion Framework
[RFC7521], and "JSON Web Token (JWT)" [JWT].
2. HTTP Parameter Bindings for Transporting Assertions
The OAuth Assertion Framework [RFC7521] defines generic HTTP
parameters for transporting assertions (a.k.a. security tokens)
during interactions with a token endpoint. This section defines
specific parameters and treatments of those parameters for use with
JWT Bearer Tokens.
2.1. Using JWTs as Authorization Grants
To use a Bearer JWT as an authorization grant, the client uses an
access token request as defined in Section 4 of the OAuth Assertion
Framework [RFC7521] with the following specific parameter values and
encodings.
The value of the "grant_type" is "urn:ietf:params:oauth:grant-
type:jwt-bearer".
The value of the "assertion" parameter MUST contain a single JWT.
The "scope" parameter may be used, as defined in the OAuth Assertion
Framework [RFC7521], to indicate the requested scope.
Authentication of the client is optional, as described in
Section 3.2.1 of OAuth 2.0 [RFC6749] and consequently, the
"client_id" is only needed when a form of client authentication that
relies on the parameter is used.
Jones, et al. Standards Track [Page 4]

RFC 7523 OAuth JWT Assertion Profiles May 2015
The following example demonstrates an access token request with a JWT
as an authorization grant (with extra line breaks for display
purposes only):
POST /token.oauth2 HTTP/1.1
Host: as.example.com
Content-Type: application/x-www-form-urlencoded
grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Ajwt-bearer
&assertion=eyJhbGciOiJFUzI1NiIsImtpZCI6IjE2In0.
eyJpc3Mi[...omitted for brevity...].
J9l-ZhwP[...omitted for brevity...]
2.2. Using JWTs for Client Authentication
To use a JWT Bearer Token for client authentication, the client uses
the following parameter values and encodings.
The value of the "client_assertion_type" is
"urn:ietf:params:oauth:client-assertion-type:jwt-bearer".
The value of the "client_assertion" parameter contains a single JWT.
It MUST NOT contain more than one JWT.
The following example demonstrates client authentication using a JWT
during the presentation of an authorization code grant in an access
token request (with extra line breaks for display purposes only):
POST /token.oauth2 HTTP/1.1
Host: as.example.com
Content-Type: application/x-www-form-urlencoded
grant_type=authorization_code&
code=n0esc3NRze7LTCu7iYzS6a5acc3f0ogp4&
client_assertion_type=urn%3Aietf%3Aparams%3Aoauth%3A
client-assertion-type%3Ajwt-bearer&
client_assertion=eyJhbGciOiJSUzI1NiIsImtpZCI6IjIyIn0.
eyJpc3Mi[...omitted for brevity...].
cC4hiUPo[...omitted for brevity...]
3. JWT Format and Processing Requirements
In order to issue an access token response as described in OAuth 2.0
[RFC6749] or to rely on a JWT for client authentication, the
authorization server MUST validate the JWT according to the criteria
below. Application of additional restrictions and policy are at the
discretion of the authorization server.
Jones, et al. Standards Track [Page 5]

RFC 7523 OAuth JWT Assertion Profiles May 2015
1. The JWT MUST contain an "iss" (issuer) claim that contains a
unique identifier for the entity that issued the JWT. In the
absence of an application profile specifying otherwise,
compliant applications MUST compare issuer values using the
Simple String Comparison method defined in Section 6.2.1 of RFC3986 [RFC3986].
2. The JWT MUST contain a "sub" (subject) claim identifying the
principal that is the subject of the JWT. Two cases need to be
differentiated:
A. For the authorization grant, the subject typically
identifies an authorized accessor for which the access token
is being requested (i.e., the resource owner or an
authorized delegate), but in some cases, may be a
pseudonymous identifier or other value denoting an anonymous
user.
B. For client authentication, the subject MUST be the
"client_id" of the OAuth client.
3. The JWT MUST contain an "aud" (audience) claim containing a
value that identifies the authorization server as an intended
audience. The token endpoint URL of the authorization server
MAY be used as a value for an "aud" element to identify the
authorization server as an intended audience of the JWT. The
authorization server MUST reject any JWT that does not contain
its own identity as the intended audience. In the absence of an
application profile specifying otherwise, compliant applications
MUST compare the audience values using the Simple String
Comparison method defined in Section 6.2.1 of RFC 3986
[RFC3986]. As noted in Section 5, the precise strings to be
used as the audience for a given authorization server must be
configured out of band by the authorization server and the
issuer of the JWT.
4. The JWT MUST contain an "exp" (expiration time) claim that
limits the time window during which the JWT can be used. The
authorization server MUST reject any JWT with an expiration time
that has passed, subject to allowable clock skew between
systems. Note that the authorization server may reject JWTs
with an "exp" claim value that is unreasonably far in the
future.
5. The JWT MAY contain an "nbf" (not before) claim that identifies
the time before which the token MUST NOT be accepted for
processing.
Jones, et al. Standards Track [Page 6]

RFC 7523 OAuth JWT Assertion Profiles May 2015
6. The JWT MAY contain an "iat" (issued at) claim that identifies
the time at which the JWT was issued. Note that the
authorization server may reject JWTs with an "iat" claim value
that is unreasonably far in the past.
7. The JWT MAY contain a "jti" (JWT ID) claim that provides a
unique identifier for the token. The authorization server MAY
ensure that JWTs are not replayed by maintaining the set of used
"jti" values for the length of time for which the JWT would be
considered valid based on the applicable "exp" instant.
8. The JWT MAY contain other claims.
9. The JWT MUST be digitally signed or have a Message
Authentication Code (MAC) applied by the issuer. The
authorization server MUST reject JWTs with an invalid signature
or MAC.
10. The authorization server MUST reject a JWT that is not valid in
all other respects per "JSON Web Token (JWT)" [JWT].
3.1. Authorization Grant Processing
JWT authorization grants may be used with or without client
authentication or identification. Whether or not client
authentication is needed in conjunction with a JWT authorization
grant, as well as the supported types of client authentication, are
policy decisions at the discretion of the authorization server.
However, if client credentials are present in the request, the
authorization server MUST validate them.
If the JWT is not valid, or the current time is not within the
token's valid time window for use, the authorization server
constructs an error response as defined in OAuth 2.0 [RFC6749]. The
value of the "error" parameter MUST be the "invalid_grant" error
code. The authorization server MAY include additional information
regarding the reasons the JWT was considered invalid using the
"error_description" or "error_uri" parameters.
Jones, et al. Standards Track [Page 7]

RFC 7523 OAuth JWT Assertion Profiles May 2015
For example:
HTTP/1.1 400 Bad Request
Content-Type: application/json
Cache-Control: no-store
{
"error":"invalid_grant",
"error_description":"Audience validation failed"
}
3.2. Client Authentication Processing
If the client JWT is not valid, the authorization server constructs
an error response as defined in OAuth 2.0 [RFC6749]. The value of
the "error" parameter MUST be the "invalid_client" error code. The
authorization server MAY include additional information regarding the
reasons the JWT was considered invalid using the "error_description"
or "error_uri" parameters.
4. Authorization Grant Example
The following examples illustrate what a conforming JWT and an access
token request would look like.
The example shows a JWT issued and signed by the system entity
identified as "https://jwt-idp.example.com". The subject of the JWT
is identified by email address as "mike@example.com". The intended
audience of the JWT is "https://jwt-rp.example.net", which is an
identifier with which the authorization server identifies itself.
The JWT is sent as part of an access token request to the
authorization server's token endpoint at "https://authz.example.net/
token.oauth2".
Below is an example JSON object that could be encoded to produce the
JWT Claims Set for a JWT:
{"iss":"https://jwt-idp.example.com",
"sub":"mailto:mike@example.com",
"aud":"https://jwt-rp.example.net",
"nbf":1300815780,
"exp":1300819380,
"http://claims.example.com/member":true}
The following example JSON object, used as the header of a JWT,
declares that the JWT is signed with the Elliptic Curve Digital
Signature Algorithm (ECDSA) P-256 SHA-256 using a key identified by
the "kid" value "16".
Jones, et al. Standards Track [Page 8]

RFC 7523 OAuth JWT Assertion Profiles May 2015
{"alg":"ES256","kid":"16"}
To present the JWT with the claims and header shown in the previous
example as part of an access token request, for example, the client
might make the following HTTPS request (with extra line breaks for
display purposes only):
POST /token.oauth2 HTTP/1.1
Host: authz.example.net
Content-Type: application/x-www-form-urlencoded
grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Ajwt-bearer
&assertion=eyJhbGciOiJFUzI1NiIsImtpZCI6IjE2In0.
eyJpc3Mi[...omitted for brevity...].
J9l-ZhwP[...omitted for brevity...]
5. Interoperability Considerations
Agreement between system entities regarding identifiers, keys, and
endpoints is required in order to achieve interoperable deployments
of this profile. Specific items that require agreement are as
follows: values for the issuer and audience identifiers, the location
of the token endpoint, the key used to apply and verify the digital
signature or MAC over the JWT, one-time use restrictions on the JWT,
maximum JWT lifetime allowed, and the specific subject and claim
requirements of the JWT. The exchange of such information is
explicitly out of scope for this specification. In some cases,
additional profiles may be created that constrain or prescribe these
values or specify how they are to be exchanged. Examples of such
profiles include the OAuth 2.0 Dynamic Client Registration Core
Protocol [OAUTH-DYN-REG], OpenID Connect Dynamic Client Registration
1.0 [OpenID.Registration], and OpenID Connect Discovery 1.0
[OpenID.Discovery].
The "RS256" algorithm, from [JWA], is a mandatory-to-implement JSON
Web Signature algorithm for this profile.
6. Security Considerations
The security considerations described within the following
specifications are all applicable to this document: "Assertion
Framework for OAuth 2.0 Client Authentication and Authorization
Grants" [RFC7521], "The OAuth 2.0 Authorization Framework" [RFC6749],
and "JSON Web Token (JWT)" [JWT].
Jones, et al. Standards Track [Page 9]

RFC 7523 OAuth JWT Assertion Profiles May 2015
The specification does not mandate replay protection for the JWT
usage for either the authorization grant or for client
authentication. It is an optional feature, which implementations may
employ at their own discretion.
7. Privacy Considerations
A JWT may contain privacy-sensitive information and, to prevent
disclosure of such information to unintended parties, should only be
transmitted over encrypted channels, such as Transport Layer Security
(TLS). In cases where it is desirable to prevent disclosure of
certain information to the client, the JWT should be encrypted to the
authorization server.
Deployments should determine the minimum amount of information
necessary to complete the exchange and include only such claims in
the JWT. In some cases, the "sub" (subject) claim can be a value
representing an anonymous or pseudonymous user, as described in
Section 6.3.1 of the OAuth Assertion Framework [RFC7521].
8. IANA Considerations8.1. Sub-Namespace Registration of urn:ietf:params:oauth:grant-type:jwt-bearer
This section registers the value "grant-type:jwt-bearer" in the IANA
"OAuth URI" registry established by "An IETF URN Sub-Namespace for
OAuth" [RFC6755].
o URN: urn:ietf:params:oauth:grant-type:jwt-bearer
o Common Name: JWT Bearer Token Grant Type Profile for OAuth 2.0
o Change Controller: IESG
o Specification Document: RFC 75238.2. Sub-Namespace Registration of urn:ietf:params:oauth:client-assertion-type:jwt-bearer
This section registers the value "client-assertion-type:jwt-bearer"
in the IANA "OAuth URI" registry established by "An IETF URN Sub-
Namespace for OAuth" [RFC6755].
o URN: urn:ietf:params:oauth:client-assertion-type:jwt-bearer
o Common Name: JWT Bearer Token Profile for OAuth 2.0 Client
Authentication
o Change Controller: IESG
o Specification Document: RFC 7523Jones, et al. Standards Track [Page 10]